Control method of air-to-water heat pump expansion valve group and air heat pump system

Abstract

The present application relates to the technical field of heat pump, and more particularly to a control method of air-source heat pump expansion valve group and an air heat pump system, the control method of air-source heat pump expansion valve group acquires the environment temperature and the condenser outlet water temperature in real time, when entering the main road supercooling bad working condition, the difference between the outlet water temperature and the outlet pipe temperature is obtained to obtain the fuzzy auxiliary road supercooling degree, the numerical value of the fuzzy auxiliary road supercooling degree judges the corresponding control to be carried out, if the fuzzy auxiliary road supercooling degree is not higher than the first set temperature value, the main expansion valve reduces the opening degree according to the first set step, and the auxiliary expansion valve is controlled according to the exhaust gas superheat degree mode; if the fuzzy auxiliary road supercooling degree is higher than the first set temperature value, and is not higher than the second set temperature value, the main expansion valve reduces the opening degree according to the first set step, and the auxiliary expansion valve is controlled according to the exhaust gas superheat degree mode. The present application can ensure that the auxiliary road takes liquid smoothly, so as to ensure the heating efficiency and prevent the alarm shutdown.

Description

Technical Field

[0001] This invention relates to the field of heat pump technology, and in particular to a control method for an air-source heat pump expansion valve assembly and an air-source heat pump system. Background Technology

[0002] like Figure 1 As shown, existing commercially available ordinary air source heat pumps rely on electric power to drive compressor 1. Compressor 1 creates a high-pressure and low-pressure system environment. Liquid refrigerant absorbs heat from the air in the low-pressure evaporator 6 and evaporates into a gaseous form. The gaseous refrigerant is then compressed by compressor 1 to become a high-pressure, high-temperature state. In condenser 2, the high-pressure, high-temperature gaseous refrigerant condenses into a liquid, simultaneously transferring heat to the water, thus heating the water. The liquid refrigerant enters the economizer 3 through the main circuit 4, and then enters the low-pressure evaporator 6 through the economizer 3 and the main expansion valve 41 to absorb heat from the air. To improve economy, a portion of the liquid refrigerant is taken from the outlet of the economizer 3 and enters the economizer 3 through the auxiliary circuit 5 and the auxiliary expansion valve 51. The liquid refrigerant entering through the auxiliary circuit 5 is heated and vaporized by the liquid refrigerant in the main circuit 4. The vaporized refrigerant then directly enters the compressor 1 for compression. Air source heat pump water heaters are electrically driven, but they do not directly heat water with electricity. Instead, they heat water by the temperature difference between the inside and outside of the pipes, ensuring water and electricity are isolated and very safe. It emits no waste gas, waste residue or other pollutants during operation, making it green and environmentally friendly.

[0003] When the ambient temperature is low and the hot water temperature is high, the heating capacity decreases significantly, resulting in a small temperature difference between the inlet and outlet of the condenser 2. Under these conditions, the liquid refrigerant is difficult to form a subcooled liquid, and the gaseous refrigerant contained in the liquid refrigerant will fill the auxiliary circuit 5, making it difficult to extract liquid from the auxiliary circuit 5. The discharge temperature of the compressor 1 is too high, causing an alarm and shutdown, thereby reducing the heating efficiency.

[0004] Therefore, a control method for the expansion valve assembly of an air-source heat pump and an air-source heat pump system are needed to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a control method for an air source heat pump expansion valve assembly and an air heat pump system, which can ensure smooth liquid intake in the auxiliary circuit, thereby ensuring heating efficiency and preventing alarm shutdowns.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The control method for the expansion valve assembly of an air source heat pump includes the following steps:

[0008] S1. Real-time acquisition of ambient temperature and condenser outlet water temperature;

[0009] S2. When the ambient temperature is not higher than -15℃ and the outlet water temperature of the condenser is higher than 45℃, it is considered a severe overcooling condition of the main pipeline, and proceed to the next step.

[0010] S3. Collect the outlet pipe temperature of the liquid refrigerant flowing out of the main pipeline through the economizer. The difference between the outlet water temperature and the outlet pipe temperature is the fuzzy auxiliary pipeline subcooling degree.

[0011] S4. Determine the undercooling degree of the fuzzy auxiliary path. If the undercooling degree of the fuzzy auxiliary path is not higher than the first set temperature value, proceed to step S5. If the undercooling degree of the fuzzy auxiliary path is higher than the first set temperature value but not higher than the second set temperature value, proceed to step S6. If the undercooling degree of the fuzzy auxiliary path is higher than the second set temperature value, proceed to step S7.

[0012] S5. The main expansion valve reduces its opening according to the first set step size. The main expansion valve is adjusted once for each first adjustable time period. The auxiliary expansion valve is controlled according to the exhaust superheat mode. Then, return to step S4.

[0013] S6. The main expansion valve reduces its opening according to the first set step size, and adjusts the main expansion valve once every second adjustable time period. The auxiliary expansion valve is controlled according to the exhaust superheat mode, and then returns to step S4.

[0014] S7. The main expansion valve enters the subcooling and overheating fuzzy control mode, and the auxiliary expansion valve is controlled according to the exhaust superheat mode. Then, the process returns to step S4 until the end.

[0015] Furthermore, in step S2, if the severe operating condition of main circuit overcooling is not met, the main expansion valve is controlled according to the intake superheat mode, and the auxiliary expansion valve is controlled according to the exhaust superheat mode.

[0016] Furthermore, the intake superheat mode control is as follows: a target intake superheat SSHs is set, the current actual intake superheat SSHs is detected, and the opening of the main expansion valve is adjusted once in each first adjustable cycle, with the number of adjustment steps = current number of steps + (SSH-SSHs)×K; where K: superheat deviation correction value.

[0017] Furthermore, the exhaust superheat mode control is as follows: set the target exhaust superheat DSHs, detect the current exhaust superheat DSH, and adjust the opening of the auxiliary expansion valve once every second adjustable cycle, with the number of adjustment steps = current number of steps + (DSH - DSHs).

[0018] Furthermore, the second adjustable duration is twice the first adjustable duration.

[0019] Further, in step S7, the supercooling and superheating fuzzy control mode is as follows: the opening degree of the main expansion valve is opened by 2% every third energy adjustment cycle until the intake superheat is the third set temperature value, the main expansion valve keeps the current opening degree unchanged, and the third set temperature value is greater than the first set temperature value and less than the second set temperature value.

[0020] Furthermore, the duration of the third adjustable period is twice the duration of the first adjustable period.

[0021] Furthermore, a first temperature sensor is installed at the outlet of the condenser.

[0022] Furthermore, a second temperature sensor is installed at the liquid refrigerant outlet of the main path of the economizer.

[0023] The air heat pump system is controlled using the control method for the air source heat pump expansion valve assembly as described above.

[0024] The beneficial effects of this invention are:

[0025] This invention provides a control method for an air-source heat pump expansion valve assembly. It collects ambient temperature and condenser outlet water temperature in real time. When the main circuit enters a subcooling condition, the method obtains the fuzzy auxiliary circuit subcooling degree based on the difference between the condenser outlet water temperature and the economizer main circuit outlet pipe temperature. The method determines the appropriate control based on the fuzzy auxiliary circuit subcooling degree. If the fuzzy auxiliary circuit subcooling degree is not higher than a first set temperature value, the main expansion valve reduces its opening by a first set step size, adjusting the main expansion valve once every first adjustable duration, while the auxiliary expansion valve is controlled according to the exhaust superheat mode. If the fuzzy auxiliary circuit subcooling degree is higher than the first set temperature value but not higher than a second set temperature value, the main expansion valve reduces its opening by a first set step size, adjusting the main expansion valve once every second adjustable duration, while the auxiliary expansion valve is controlled according to the exhaust superheat mode. If the fuzzy auxiliary circuit subcooling degree is higher than the second set temperature value, the main expansion valve enters a subcooling / overheating fuzzy control mode, while the auxiliary expansion valve is controlled according to the exhaust superheat mode. By adopting the above control strategy, when the subcooling degree of the main circuit is low under severe subcooling conditions, the opening of the main expansion valve is reduced to increase the subcooling degree of the refrigerant outlet of the condenser. This allows some liquid refrigerant to enter the economizer through the auxiliary circuit, where it vaporizes and then enters the compressor. This effectively ensures that the auxiliary circuit can smoothly obtain liquid refrigerant, ensuring the normal operation of the compressor, thereby guaranteeing heating efficiency and preventing alarm shutdowns.

[0026] The air heat pump system provided by this invention uses the control method of the air source heat pump expansion valve group as described above to ensure smooth liquid intake in the auxiliary circuit, thereby ensuring heating efficiency and preventing alarm shutdown. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an air heat pump system;

[0028] Figure 2 This is a flowchart of a control method for an air-source heat pump expansion valve assembly according to the present invention.

[0029] In the picture:

[0030] 1. Compressor; 2. Condenser; 21. First temperature sensor; 22. Second temperature sensor; 3. Economizer; 4. Main circuit; 41. Main expansion valve; 5. Auxiliary circuit; 51. Auxiliary expansion valve; 6. Low-pressure evaporator. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings, not all of them.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] When an air heat pump system operates at a lower ambient temperature and a higher hot water temperature, the heating capacity decreases significantly, resulting in a smaller temperature difference between the refrigerant inlet and outlet of the condenser. Under these conditions, it is difficult for the liquid refrigerant to form a subcooled liquid.

[0035] To address the aforementioned issues and ensure smooth liquid intake in the auxiliary circuit, thereby guaranteeing heating efficiency and preventing alarm shutdowns, such as... Figures 1-2As shown, this invention provides a control method for an air source heat pump expansion valve assembly. The control method for the air source heat pump expansion valve assembly includes the following steps:

[0036] S1. Real-time acquisition of ambient temperature and outlet water temperature of condenser 2;

[0037] S2. When the ambient temperature is not higher than -15℃ and the outlet water temperature of condenser 2 is higher than 45℃, it is considered a severe overcooling condition of the main pipeline, and proceed to the next step.

[0038] S3. Collect the outlet pipe temperature of the liquid refrigerant flowing out of the main road 4 at point 3 of the economizer. The difference between the outlet water temperature and the outlet pipe temperature is the fuzzy auxiliary road subcooling degree.

[0039] S4. Determine the fuzzy auxiliary path undercooling. If the fuzzy auxiliary path undercooling is not higher than the first set temperature value, proceed to step S5. If the fuzzy auxiliary path undercooling is higher than the first set temperature value but not higher than the second set temperature value, proceed to step S6. If the fuzzy auxiliary path undercooling is higher than the second set temperature value, proceed to step S7.

[0040] S5. The main expansion valve 41 reduces its opening according to the first set step size. The main expansion valve 41 is adjusted once for each first adjustable time period. The auxiliary expansion valve 51 is controlled according to the exhaust superheat mode. Then return to step S4.

[0041] S6. The main expansion valve 41 reduces its opening according to the first set step size. The main expansion valve 41 is adjusted once every second adjustable time. The auxiliary expansion valve 51 is controlled according to the exhaust superheat mode. Then return to step S4.

[0042] S7. The main expansion valve 41 enters the subcooling and overheating fuzzy control mode, and the auxiliary expansion valve 51 is controlled according to the exhaust superheat mode. Then, return to step S4 until the end.

[0043] By adopting the above control strategy, when the subcooling degree of the main circuit 4 is low under the severe subcooling conditions of the main circuit, the opening of the main expansion valve 41 is reduced to increase the subcooling degree of the refrigerant outlet of the condenser. This allows some liquid refrigerant to enter the economizer 3 through the auxiliary circuit 5, where it vaporizes and enters the compressor 1. This effectively ensures that the auxiliary circuit 5 can smoothly obtain liquid refrigerant, ensuring the normal operation of the compressor 1, thereby guaranteeing heating efficiency and preventing alarm shutdowns.

[0044] Further, in step S2, if the main circuit subcooling severe operating condition is not met, the main expansion valve 41 is controlled according to the suction superheat mode, and the auxiliary expansion valve 51 is controlled according to the discharge superheat mode. The temperature increase after the liquid refrigerant absorbs heat from the environment is called suction superheat, which is calculated as suction temperature - temperature of the low-pressure evaporator 6. Discharge superheat is the temperature difference between the temperature of the refrigerant inlet of the compressor 1 or condenser 2 and the saturation temperature corresponding to the actual refrigerant condensing pressure. When the air heat pump system is not under the main circuit subcooling severe operating condition, it can be controlled normally. The normal operation of the air heat pump system is ensured by dynamically adjusting the opening of the main expansion valve 41 and the auxiliary expansion valve 51.

[0045] Furthermore, the intake superheat mode control is as follows: a target intake superheat SSHs is set, the current actual intake superheat SSHs is detected, and the opening of the main expansion valve 41 is adjusted once every first adjustable cycle. The number of adjustment steps each time = current number of steps + (SSH - SSHs) × K; where K: superheat deviation correction value. In this embodiment, the value of K is 1 by default, and the duration of the first adjustable cycle is 20s. In other embodiments, the value of K and the duration of the first adjustable cycle can also be set according to actual needs, without further restrictions. By dynamically adjusting the opening of the main expansion valve 41, the normal operation of the air heat pump system can be ensured.

[0046] Furthermore, the exhaust superheat mode control is as follows: a target exhaust superheat DSHs is set, the current exhaust superheat DSHs is detected, and the opening of the auxiliary expansion valve 51 is adjusted once every second adjustable cycle, with the number of adjustment steps equal to the current number of steps plus (DSH - DSHs). In this embodiment, the duration of the second adjustable cycle is 10 seconds. By dynamically adjusting the opening of the auxiliary expansion valve 51, the normal operation of the air heat pump system can be ensured.

[0047] Furthermore, the second adjustable duration is twice the first adjustable duration. Through the above design, when the subcooling degree of the fuzzy auxiliary circuit is low, the opening of the main expansion valve 41 is reduced rapidly, so that the liquid refrigerant can effectively flow into the auxiliary circuit 5. After achieving a certain adjustment effect, the adjustment duration is extended, thereby reducing the speed of the main expansion valve 41 opening adjustment.

[0048] Further, in step S7, the fuzzy control mode for subcooling and overheating is as follows: the opening degree of the main expansion valve 41 is increased by 2% every third adjustable cycle until the suction superheat reaches the third set temperature value. The main expansion valve 41 then maintains its current opening degree. The third set temperature value is greater than the first set temperature value and less than the second set temperature value. By adjusting in this way, the main expansion valve 41 can be placed at a suitable opening degree, thereby ensuring the normal operation of the air heat pump system. In this embodiment, the first set temperature value is 5℃, the second set temperature value is 10℃, and the third set temperature value is 8℃.

[0049] Furthermore, the duration of the third adjustment cycle is twice that of the first adjustment cycle. Since entering the supercooling and superheating fuzzy control mode requires fine-tuning of the opening of the main expansion valve 41, extending the duration of the third adjustment cycle can reduce the adjustment speed and achieve fine adjustment of the main expansion valve 41.

[0050] Furthermore, a first temperature sensor 21 is installed at the outlet of the condenser 2. By installing the first temperature sensor 21, the temperature at the outlet of the condenser 2 can be collected in real time.

[0051] Furthermore, a second temperature sensor 22 is installed at the liquid refrigerant outlet of the main circuit 4 at the economizer 3. By installing the second temperature sensor 22, the temperature at the liquid refrigerant outlet of the condenser 2 can be collected in real time.

[0052] This embodiment also provides an air heat pump system, which is controlled by the air source heat pump expansion valve group control method described above. This ensures that the auxiliary circuit 5 can smoothly extract liquid, thereby ensuring heating efficiency and preventing alarm shutdowns.

[0053] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A control method for an air source heat pump expansion valve assembly, characterized in that, Includes the following steps: S1. Real-time acquisition of ambient temperature and outlet water temperature of condenser (2); S2. When the ambient temperature is not higher than -15℃ and the outlet water temperature of the condenser (2) is higher than 45℃, it is considered as a severe overcooling condition of the main pipeline, and the next step is carried out. S3. Collect the outlet temperature of the liquid refrigerant flowing out of the main road (4) at the economizer (3). The difference between the outlet water temperature and the outlet pipe temperature is the fuzzy auxiliary road subcooling degree. S4. Determine the undercooling degree of the fuzzy auxiliary path. If the undercooling degree of the fuzzy auxiliary path is not higher than the first set temperature value, proceed to step S5. If the undercooling degree of the fuzzy auxiliary path is higher than the first set temperature value but not higher than the second set temperature value, proceed to step S6. If the undercooling degree of the fuzzy auxiliary path is higher than the second set temperature value, proceed to step S7. S5. The main expansion valve (41) reduces its opening according to the first set step size. The main expansion valve (41) is adjusted once for each first adjustable time period. The auxiliary expansion valve (51) is controlled according to the exhaust superheat mode. Then, the process returns to step S4. S6. The main expansion valve (41) reduces its opening according to the first set step size, and adjusts the main expansion valve (41) once for each second adjustable time period. The auxiliary expansion valve (51) is controlled according to the exhaust superheat mode, and then returns to step S4. S7. The main expansion valve (41) enters the supercooling and superheating fuzzy control mode, and the auxiliary expansion valve (51) is controlled according to the exhaust superheat mode. Then, it returns to step S4 until the end. The second adjustable duration is twice the first adjustable duration; In step S7, the supercooling and superheating fuzzy control mode is as follows: the opening degree of the main expansion valve (41) is opened by 2% every third energy adjustment cycle until the intake superheat is the third set temperature value. The main expansion valve (41) keeps the current opening degree unchanged. The third set temperature value is greater than the first set temperature value and less than the second set temperature value.

2. The control method for the air source heat pump expansion valve assembly according to claim 1, characterized in that, In step S2, if the main circuit is not undercooled and the severe operating condition is not met, the main expansion valve (41) is controlled in the intake superheat mode, and the auxiliary expansion valve (51) is controlled in the exhaust superheat mode.

3. The control method for the air source heat pump expansion valve assembly according to claim 2, characterized in that, The intake superheat mode control is as follows: set the target intake superheat SSHs, detect the current actual intake superheat SSH, and adjust the opening of the main expansion valve (41) once in each first adjustable cycle. The number of adjustment steps each time is = the current number of steps + (SSH-SSHs) × K; where K is the superheat deviation correction value.

4. The control method for the air source heat pump expansion valve assembly according to claim 1, characterized in that, The duration of the third energy-adjustable cycle is twice the duration of the first energy-adjustable cycle.

5. The control method for the air source heat pump expansion valve assembly according to claim 1, characterized in that, A first temperature sensor (21) is installed at the outlet of the condenser (2).

6. The control method for the air source heat pump expansion valve assembly according to claim 1, characterized in that, A second temperature sensor (22) is installed at the liquid refrigerant outlet of the main road (4) at the economizer (3).

7. An air heat pump system, characterized in that, The control is performed using the control method for the air source heat pump expansion valve assembly as described in any one of claims 1-6.

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